Heart System
Each day, the average human heart beats about 100,000 times, pumping 2,000 gallons of blood through the body. That's a lot of work for an organ no bigger than a large fist and weighing 8 to 12 ounces. LISTEN UP: Add the new Michigan Medicine News Break to your Alexa-enabled device, or subscribe to our daily audio updates on iTunes, Google Play and Stitcher. In fact, the heart does more physical work than any other muscle over a lifetime.
Located between the lungs in the middle of the chest, the heart pumps blood through the network of arteries and veins known as the cardiovascular system. It pushes blood to the body’s organs, tissues and cells. Blood delivers oxygen and nutrients to every cell and removes the carbon dioxide and other waste products made by those cells. Blood is carried from the heart to the rest of the body through a complex network of arteries, arterioles and capillaries. Blood is returned to the heart through venules and veins.
Parts of the human heart
The heart is made up of four chambers: two upper chambers known as the left atrium and right atrium and two lower chambers called the left and right ventricles.
It is also made up of four valves: the tricuspid, pulmonary, mitral and aortic valves.
The right atrium receives non-oxygenated blood from the body's largest veins — superior vena cava and inferior vena cava — and pumps it through the tricuspid valve to the right ventricle.
The right ventricle pumps the blood through the pulmonary valve to the lungs, where it becomes oxygenated.
The left atrium receives oxygenated blood from the lungs and pumps it through the mitral valve to the left ventricle.
The left ventricle pumps oxygen-rich blood through the aortic valve to the aorta and the rest of the body.
Anterior chamber of eyeball
The anterior chamber is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Aqueous humor is the fluid that ftlls the anterior chamber. Hyphema and glaucoma are two main pathologies in this area.
In hyphema, blood fills the anterior chamber. In glaucoma, blockage of the canal of Schlemm prevents the normal outflow of aqueous humor, resulting in accumulation of fluid, increased intraocular pressure, and eventually blindness.
One peculiar feature of the anterior chamber is dampened immune response to allogenic grafts. This is called anterior chamber associated immune deviation (ACAID), a term introduced in 1981 by Streilein et al
Tenon's capsule
The fascia bulbi (also known as the capsule of Ténon and the bulbar sheath) is a thin membrane which envelops the eyeball from the optic nerve to the limbus, separating it from the orbital fat and forming a socket in which it moves.
[ts inner surface is smooth, and is separated from the outer surface of the sclera by the periscleral lymph space.
This lymph space is continuous with the subdural and subarachnoid cavities, and is traversed by delicate bands of connective tissue which extend between the fascia and the sclera.
The fascia is perforated behind by the ciliary vessels and nerves, and fuses with the sheath of the optic nerve and with the sclera around the entrance of the optic nerve.
In front it adheres to the conjunctiva, and both structures are attached to the ciliary region of the eyeball.
The structure was named after Jacques-René Tenon (1724-1816), a French surgeon and pathologist.
Central retinal artery
The central retinal artery (retinal artery) branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.
Course
It pierces the optic nerve close to the eyeball, sending branches over the internal surface of the retina, and these terminal branches are the only blood supply to the larger part of it. The central part of the retina where the light rays are focussed after passing through the pupil and the lens is a circular area called the macula. The center of this circular area is the fovea. The fovea and a small area surrounding it are not supplied by the central retinal artery or its branches, but instead by the choroid.
Central retinal vein
The central retinal vein (retinal vein) is a short vein that runs through the optic nerve and drains blood from the capillaries of the retina into the larger veins outside the eye. The anatomy of the veins of the orbit of the eye varies between individuals, and in some the central retinal vein drains into the superior ophthalmic vein, and in some it drains directly into the cavernous sinus